Page-align the read/write buffer. Unclear if this helps, but

it certainly doesn't hurt.

src/iperf.h

@@ -84,7 +84,8 @@ struct iperf_stream
     struct iperf_stream_result *result;	/* structure pointer to result */
     Timer     *send_timer;
     int       udp_green_light;
-    char      *buffer;		/* data to send */
+    char      *buffer_malloc;	/* data to send, malloced */
+    char      *buffer;		/* data to send, page-aligned */
 
     /*
      * for udp measurements - This can be a structure outside stream, and

src/iperf_api.c

@@ -1673,7 +1673,7 @@ iperf_free_stream(struct iperf_stream *sp)
     struct iperf_interval_results *irp, *nirp;
 
     /* XXX: need to free interval list too! */
-    free(sp->buffer);
+    free(sp->buffer_malloc);
     for (irp = TAILQ_FIRST(&sp->result->interval_results); irp != TAILQ_END(sp->result->interval_results); irp = nirp) {
         nirp = TAILQ_NEXT(irp, irlistentries);
         free(irp);
@@ -1684,6 +1684,11 @@ iperf_free_stream(struct iperf_stream *sp)
     free(sp);
 }
 
+#define PAGE 65536
+/* A guess - we should actually detect real page size.  But as long as
+** this is a multiple of the real one, it works for alignment purposes.
+*/
+
 /**************************************************************************/
 struct iperf_stream *
 iperf_new_stream(struct iperf_test *test, int s)
@@ -1700,11 +1705,11 @@ iperf_new_stream(struct iperf_test *test, int s)
     memset(sp, 0, sizeof(struct iperf_stream));
 
     sp->test = test;
-    sp->buffer = (char *) malloc(test->settings->blksize);
+    sp->buffer_malloc = (char *) malloc(test->settings->blksize + PAGE);
     sp->result = (struct iperf_stream_result *) malloc(sizeof(struct iperf_stream_result));
     sp->settings = test->settings;
 
-    if (!sp->buffer) {
+    if (!sp->buffer_malloc) {
         i_errno = IECREATESTREAM;
         return NULL;
     }
@@ -1717,6 +1722,7 @@ iperf_new_stream(struct iperf_test *test, int s)
     TAILQ_INIT(&sp->result->interval_results);
     
     /* Randomize the buffer */
+    sp->buffer = (char*) (((uint64_t) sp->buffer_malloc / PAGE + 1 ) * PAGE);
     srandom(time(NULL));
     for (i = 0; i < test->settings->blksize; ++i)
         sp->buffer[i] = random();